High‐Performance and Industrially Viable Nanostructured SiO_x Layers for Interface Passivation in Thin Film Solar Cells

Abstract

Herein, it is demonstrated, by using industrial techniques, that a passivation layer with nanocontacts based on silicon oxide (SiOx) leads to significant improvements in the optoelectronical performance of ultrathin Cu(In,Ga)Se2 (CIGS) solar cells. Two approaches are applied for contact patterning of the passivation layer: point contacts and line contacts. For two CIGS growth conditions, 550 and 500 °C, the SiOx passivation layer demonstrates positive passivation properties, which are supported by electrical simulations. Such positive effects lead to an increase in the light to power conversion efficiency value of 2.6% (absolute value) for passivated devices compared with a nonpassivated reference device. Strikingly, both passivation architectures present similar efficiency values. However, there is a trade‐off between passivation effect and charge extraction, as demonstrated by the trade‐off between open‐circuit voltage (Voc) and short‐circuit current density (Jsc) compared with fill factor (FF). For the first time, a fully industrial upscalable process combining SiOx as rear passivation layer deposited by chemical vapor deposition, with photolithography for line contacts, yields promising results toward high‐performance and low‐cost ultrathin CIGS solar cells with champion devices reaching efficiency values of 12%, demonstrating the potential of SiOx as a passivation material for energy conversion devices.

Exploiting the Optical Limits of Thin‐Film Solar Cells: A Review on Light Management Strategies in Cu(In,Ga)Se2

“…However, Mo use is a tradeoff, as the low interface reflectivity (<20%) achieved with the Mo/MoSe 2 and CIGS system compromises the optical path length enhancement. [ 42,181 ] Several approaches have been developed to replace the Mo rear contact by a more optically favorable configuration, ranging from 1) a direct metallic layer replacement; [ 179,182–186 ] 2) addition of a nanostructured reflective passivation layer; [ 36,187–190 ] 3) through the coupling of a metallic reflective layer with a point‐contact passivation architecture; [ 191,192 ] or 4) different combinations of TCOs and metallic rear reflectors. [ 55,193–195 ] Nonetheless, this is not a simple task, as a great variety of requirements must be fulfilled to attain a viable rear contact, such as thermal, chemical, and mechanical stability, low interface recombination, and the ability to achieve an ohmic contact.…”

“…[ 35 ] Thus, other strategies, such as patterned dielectric layers, have been studied. [ 36–40 ] Moreover, in ultrathin solar cells, the absorber thickness value is lower than the optical thickness required to fully absorb the incoming light, resulting in high optical losses, which leads to a short‐circuit current density ( J sc ) value decrease. [ 41–43 ]…”

Natural Waste to Electricity: Engineering Pomegranate Peels and Ag-Doped ZnO for Photovoltaic Applications

“…In spite of monopoly by silicon solar cells, they suffer some disadvantages like, the cost of production and absorption of sunlight in only red light of solar energy (Pizzini 2010, Wenham &Green 1996. This requires new materials and technologies for the wide absorption of sunlight and without increasing the power production cost (Beard et al 2014, Chalkias et al 2021, Cunha et al 2021, Kokkonen et al 2021, Vlachopoulos et al 2021.…”

Is a passivated back contact always beneficial for Cu (In,Ga)Se2 solar cells?

“…Up to now, the relevant explorations of passivating back contacts have mainly been confined to cells on Mo with an Ohmic contact. [8][9][10][11][12][13][14][15][16][17][18] Since cells on TCOs may exhibit a Schottky-like back contact with a barrier potential, this may bring a different carrier transport behavior from the condition with an Ohmic contact. Further, considering promising applications and relatively poor performance of ultrathin CIGSe solar cells on TCOs, it will be of great interest to identify how a passivated back contact affects CIGSe solar cells with a Schottky back contact.…”

“…Besides, ultrathin CIGSe solar cells exhibit a less pronounced current suppression in contrast to thick cells. Those results indicate that the simple assumption of a homojunction cell is reasonable enough to explore effects of the back Schottky diode on CIGSe solar cells and interpretations deduced from the simple homojunction model are relevant for realistic CIGSe solar cells.Introducing point-contact nanostructures for passivating the back contact in ultrathin CGISe solar cells was intensively explored on Mo, and a significant improvement of electrical properties was validated [8][9][10][11][12][13][14][15][16][17][18]. In contrast to this case of an Ohmic back contact, CIGSe solar cells on TCO substrates are typically treated having a Schottky-like back contact with a back barrier potential.…”